Bernd, Are you ok with the explanation and existing changes ?
-Sharath Ballal From: Sharath Ballal Sent: Friday, November 11, 2016 12:17 PM To: Bernd Eckenfels; [email protected] Subject: RE: RFR: JDK-7107013: sun.jvm.hotspot.runtime.Bytes.swapLong conversion to long mishandled Hello Bernd, 45 return (short) (((x >> 8) & 0xFF) | (x << 8)); Or return (short)((x << 8) | ((x >> 8) & 0xFF)); In the above two lines of code, whichever you choose to write, they both will give the same result. Short will be implicitly converted to int and then the operation will take place. If you write the code as below (to make it consistent with int and long), you will get an error saying “possible lossy conversion from int to short” return ((short) (x << 8) | ((x >> 8) & 0xFF)); or return ((short) (x << 8) | (short)((x >> 8) & 0xFF)); So an explicit cast will be required in both the above cases. Let me know if you would want to see the code changed to “return (short)((x << 8) | ((x >> 8) & 0xFF));” to make it look consistent with the rest of the code. (Since I was not in to/cc, it took me longer to see the mail) -Sharath Ballal From: Bernd Eckenfels [mailto:[email protected]] Sent: Thursday, November 10, 2016 2:12 PM To: HYPERLINK "mailto:[email protected]"[email protected] Subject: Re: RFR: JDK-7107013: sun.jvm.hotspot.runtime.Bytes.swapLong conversion to long mishandled Hello, I was talking about the code order not the semantics: 45 return (short) (((x >> 8) & 0xFF) | (x << 8)); 54 return ((int)swapShort((short) x) << 16) | (swapShort((short) (x >> 16)) & 0xFFFF); 63 return ((long)swapInt((int) x) << 32) | (swapInt((int) (x >> 32)) & 0xFFFFFFFF); In 45 the Low half is expressed first (and no masking) in 54 and 63 the MSB half is expressed first. I guess casting and masking and order should be the same for all 3? Gruss Bernd -- http://bernd.eckenfels.net On Thu, Nov 10, 2016 at 9:30 AM +0100, "Sharath Ballal" <HYPERLINK "mailto:[email protected]"; \[email protected]> wrote: Hello Bernd, For int also its “low 2 bytes | high 2 bytes” and again these two byte pairs are swapped by the swapshort as “lowbyte | highbyte” Similarly for long its “ low 4 bytes | high 4 bytes” and again these pairs are swapped recursively. So for int if the little endian byte order was 3 2 1 0 it is now converted to 0 1 2 3 and similarly for long. -Sharath Ballal From: Bernd Eckenfels [mailto:[email protected]] Sent: Thursday, November 10, 2016 1:20 PM To: HYPERLINK "mailto:[email protected]"[email protected]; Dmitry Samersoff; Sharath Ballal Subject: Re: RFR: JDK-7107013: sun.jvm.hotspot.runtime.Bytes.swapLong conversion to long mishandled Hello, Is the a reason why swapShort has a " lowbyte | highbyyte" and the other two methods the other way around? I would all write in the natural order of. Igendianess (I.e. Change the first). Gruss Bernd -- http://bernd.eckenfels.net On Thu, Nov 10, 2016 at 8:32 AM +0100, "Sharath Ballal" <HYPERLINK "mailto:[email protected]"; \[email protected]> wrote: Thanks Dmitry. I have made the changes in line 54. http://cr.openjdk.java.net/~sballal/7107013/webrev.01/ I didn't change the recursive calls to swap functions because that looks more readable. -Sharath Ballal -----Original Message----- From: Dmitry Samersoff Sent: Thursday, November 10, 2016 12:46 AM To: Sharath Ballal; HYPERLINK "mailto:[email protected]"[email protected] Subject: Re: RFR: JDK-7107013: sun.jvm.hotspot.runtime.Bytes.swapLong conversion to long mishandled Sharath, Please, add (int) to ll. 54 for better readability. PS: Despite the fact that C2 does a great job eliminating useless code (multiple calls to if (!swap) in this case) it would be nice to use simple, well known arithmetic directly instead of subsequent calls to other swap functions. -Dmitry On 2016-11-09 19:30, Sharath Ballal wrote: > Hello, > > Pls review this small fix > > > > Issue: https://bugs.openjdk.java.net/browse/JDK-7107013 > > Webrev: http://cr.openjdk.java.net/~sballal/7107013/webrev.00/ > > > > > > -Sharath Ballal > > > > > -- Dmitry Samersoff Oracle Java development team, Saint Petersburg, Russia * I would love to change the world, but they won't give me the sources.
